Vibrating-type screening machines typically have vibrating mechanism operatively connected to deck frames which support screen media. In many such machines, the screen media is tightly held by side tensioning and supported below by a suitable structure typically imparting a curved shape to the screen media. This involves employing tensioning assemblies affixed to side plates which stand tall of the deck frame. A typical side tensioning assembly includes a tension rail fastened to the side plate using fastening hardware. The tension is configured to engage tensioning hooks connected to side edges of the screen media. When deployed, the tension rail applies a tensile force on the tensioning hooks which operates to draw the screen media down toward the deck frame and outward toward the side plate.
In some tensioning assemblies, the direction of the tensile force can be adjusted using an angle box mounted to the outer surface of the side plate. The angle box has a wedge-like structure which has an oblong opening formed therein that is configured to communicate with an aperture defined in the side plate. The oblong opening in the wedge-like structure and the aperture defined in the side plate are aligned to receive therethrough a bolt having a particular angled orientation which corresponds to the desired direction in which the tensile force is to be applied. The bolt is part of the fastening hardware that is used to tie the tension rail to the side plate.
In a typical installation of such a tensioning assembly, the bolt is first fitted through an aperture formed in the tension rail. The remaining portion of the bolt is inserted through the aperture defined in the side plate and extends through the oblong opening in the angle box. The terminal end of the bolt protrudes from the angle box away from the side plate, where a washer and nut engage the bolt. In order to create the requisite tension to retain the screen media, the nut is tightened against the washer which sits between the angle box and the nut.
Such tensioning assemblies tend to be effective in tightly retaining the screen media between the side plates. However, concerns have been expressed regarding the number of loose parts in such tensioning assemblies. More specifically, in the tensioning assembly of the type described above, the fastening hardware includes a bolt, a nut and a washer, and then there is also the tension rail. Some vibrating-type screen machines can be quite large and have multiple deck frames stacked one over the other. Such machines tend to require many sections of tension rail and many tensioning assemblies, thereby further exacerbating the problem of having too many loose parts. Such parts take time to assemble and can easily be dropped, mishandled or lost, thereby leading to increased downtime of the machine while the screen media is being replaced. As a result, a steady supply of replacement fastening hardware must be kept on hand. This can be a serious disadvantage in applications which require frequent replacement of the screen media due to wear and tear or other reasons. All the more so, because such screen media maintenance or service activities typically require two workmen to carry them out.
In light of the foregoing, it would be advantageous to have a tensioning assembly which can easily be deployed rapidly and with ease, and which obviates the above-described drawbacks associated with known tensioning assemblies that employ angle boxes.